The proposed research aims at studying the clinical, microbiological, and histopathological features of repeated experimental periodontitis in beagle dogs. The main objective is to study whether a long junctional epithelium (as a result of periodontal therapy) is any more vulnerable to destruction than a connective tissue attachment. Plaque scores, gingivitis scores, pocket depth, attachment level, phase contrast microscopy of subgingival plaque samples, radiographs, and the inflammatory cell infiltrate will be the parameters studied at regular intervals. Experimentyal pockets will wb created on premolars of one side of the mouth in five beagle dogs using a modified band and ligature mthod. After six months of initial induction, the diseased half will be treated by flap crettage procedures to leave a long junctional epithelium as the attachment mechanism. After three months of repeated prophylaxis and plaque control during the post-surgical phase, plaque will be allowed to accumulate for six months on both treated (experimental) and untreated (control) sides. Orthodontic brackets cemented supragingivally will serve to retain plaque formed by feeding a soft, sticky diet. The dogs will be sacrificed after the six month plaque accumulation period, and block sections removed for histopathologic study. The features of repeated experimental periodontitis on the previously treated side will be compared with those of the side su bjected to disease for the first time.